External USB hard drive enclosure problem

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KSMike

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Nov 1, 2007
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Hello,

I have a pair of identical external USB drive enclosures. They're both Dynex DX-HDEN10 enclosures. One is just a spare. I've been using a WD 250GB drive in one of them for about a year without any problems. A few days ago I turned it on and it sounded as though the power was being interrupted to the drive momentarily, every 5-10 seconds. As a troubleshooting measure I moved the drive over to the spare enclosure and connected it to the same original power supply. It worked fine.

Assuming there was a power problem in the first enclosure, I connected it back to the same power supply (without the drive) and attached my DMM at the Molex connector. On the +12V line I get about +12.5V. On the +5V line I only get about +4.6V, but that's still within a 10% tolerance (barely).

I thought the low voltage on the +5V line might be the culprit, so I attached the DMM to the spare enclosure in the same way (removed the drive, used the same power supply). The voltage supplied on both lines was identical to the first enclosure! So now I have one power supply feeding either of two identical enclosures, and the resulting voltage at the Molex plug is identical in both. Yet, one enclosure keeps cycling the drive and the other doesn't. My Fluke DMM has a min/max/avg function, and in all tests I let it monitor the voltage for a couple of minutes on the "min" setting so I could see whatever the lowest voltage was.

What might I be overlooking? I know these enclosures are dirt cheap and not worth my time messing with, but it has become a "mission" for me to figure this out. I've tried to find a schematic or other technical documentation for the board in these enclosures, without success.

Thanks for any help!

Mike
 
Joined
Sep 1, 2007
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194
Sounds like it could just be a cold solder joint to me... but that's just a guess. If you can't find any, you could simply reflow all the solder points you can get to easily, and hope that does the trick... Without a schematic, I really can't help you much... Best of luck tracking this down...
 

fairnooks

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Oct 1, 2007
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5,251
I didn't follow your explanation of troubleshooting measures very well but in case the following is a possibility I included it.

Do the external drive cases have a power flip switch? If so there's a copper rocker inside and sometimes the tension or pressure is not strong enough and it will cycle the power as the connection is borderline. I solved this problem by popping the swtich out and bending the copper rocker a little bit more so there was a nice strong snap to the power position and it has worked great ever since.
 

KSMike

Thread Starter
Joined
Nov 1, 2007
Messages
3
Sorry for the confusion. Basically I have two identical enclosures, both reading a good strong +12V and a weak +5V (but both are identically weak). Neither, according to my tests, is intermittent on power to the drive. Yet, in actual use one of them appears to have just such an intermittency. They do have rocker switches, but again I'm testing at the Molex plug, the last stop before the drive itself, and I'm not seeing any drops. I did inspect for cold solder joints etc. and didn't see anything. Strange.
 

mrss

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Jun 13, 2007
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722
Sounds like you checked the supply power with nothing attached? Try it with the drive connected and trying to draw power. I bet you'll find a voltage fall off on the bad power supply.
 

KSMike

Thread Starter
Joined
Nov 1, 2007
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3
mrss, that makes sense. Didn't test with a load. I'll try it, thanks! And thanks for the other replies, too.
 
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